1. Field of the Invention
This invention relates to methanation catalysts suitable for methanating naturally occurring liquid hydrocarbons or synthetic liquid hydrocarbons, prepared from solid carbonaceous materials, to produce synthetic fuel gas. The method of preparation involves sequentially impregnating an inorganic refractory oxide support or matrix with either Group IV(B), V(B) or VI(B) metals in combination with Group VIII metals of the Periodic Table.
Around the turn of the century, coal was displaced as an energy source by oil and gas in the commercial and, to a large extent, the residential markets because it was more difficult to handle than other fuels and, additionally, leaves a residue that must be disposed of in the form of dirt and dust.
The shrinking petroleum and natural gas reserves around the world, increased demand and recently enacted governmental sulfur oxides emission standards in the United States, have highlighted the need to focus attention on clean burning synthetic fuels which approximate the properties and characteristics of natural gas.
Presently, utility companies which supply and distribute natural fuel gas for residential and commercial use have an increasingly acute need for an economical method of supplying fuel gas during peak-load periods, especially in frigid areas that depend upon natural gas to heat residential units. During cold weather, demand for fuel gas may be double or triple the volume used on a mild day. One method of meeting the peak-load demand is to add propane-air mixtures to the gas. However, the amount of propane-air that may be added to gas is limited and there is a real need for an economical process that can be used to supply peak-load demand for fuel gas.
Fossil fuels, which took nature millions of years to form, are currently being consumed at such prodigious rates that petroleum and gas supplies may be good for only 50 to 70 more years and coal supplies for two or three more centuries. World wide accelerating demand for fuel has contributed to the present energy crisis. Natural gas, typically, contains about 94.9 percent methane. Since natural gas appears to be the most scarce of the fossil fuels, the development of an economical process for producing synthetic natural gas or substantially pure methane from either solid or liquid hydrocarbons is of considerable importance.
2. Description of the Prior Art
Processes and catalysts for the gasification of liquid hydrocarbons and carbonaceous materials to produce synthetic fuel gas are known and appreciated by the prior art. For example, U.S. Pat. No. 3,928,000 discloses a process for converting hydrocarbonaceous materials into a clean methane-rich gas stream which may be burned as a fuel. Particularly, a hydrocarbonaceous fuel is gasified by partial oxidation to produce a process gas stream which is cooled, cleaned and subjected to catalytic methanation over a sulfur-resistant catalyst comprising Co, Cr, W, Mo or Ni and mixtures thereof supported on a structure formed from Group III and IV elements; for example, alumina, silica, zeolite, etc.
Another process is disclosed in U.S. Pat. No. 3,712,800 which relates to a method for converting residual oils into fuel gas. The method consists of contacting an oil feed, under methanation conditions, with a metallic modifying agent which contains vanadium, nickel, or a dispersible iron compound, and mixtures thereof.
U.S. Pat. No. 4,065,514 relates to a process for preparing methane using a catalyst consisting of a silica-alumina support composited with an iron group metal in combination with a metal of the platinum-palladium group wherein each of said metals is substantially uniformly distributed throughout the body of said support.
U.S. Pat. No. 3,506,417 discloses a process for the production of methane-containing gases from propane feedstocks which comprises contacting a propane feedstock and steam, under methanation conditions, with a catalyst selected from (a) a silica supported nickel or (b) a supported platinum group metal, both promoted with an alkali metal or alkaline earth metal. The gases thus produced are said to be fungible with natural gas.
Another process for methane synthesis is set forth in U.S. Pat. No. 3,930,812, which relates to a process for the catalytic production of methane from carbon oxides and hydrogen, which are produced from the gasification of fossil fuels or aliphatic alcohols with steam and/or oxygen. Particularly, the reference teaches the reaction of an alcohol, for example methanol, with steam and/or oxygen over an iron oxide/chromium oxide catalyst to provide a feedstock for further methanation. The feedstock thus produced is contacted, under methanation conditions, with a catalyst comprising raney nickel and metals of Group VIII of the Periodic Table.
U.S. Pat. No. 4,039,302 relates to a process and catalyst suitable for synthesizing low boiling aliphatic hydrocarbons (C.sub.1 to C.sub.3) from carbon monoxide and hydrogen. The carbon monoxide and hydrogen are obtained from materials such as bituminous coal, lignite, oil shale, crude oil and fuel oils using conventional techniques. Low boiling aliphatic hydrocarbons are prepared by contacting carbon monoxide and hydrogen with a catalyst comprising an interspersed mixture of cobalt oxide, aluminum oxide, zinc oxide and molybdenum oxide under reaction conditions.
A methane-rich gas process is disclosed in U.S. Pat. No. 3,927,999 which relates to the catalytic methanation of synthesis gas feed comprising hydrogen and carbon monoxide obtained from the gasification of a solid carbonaceous material or a liquid hydrocarbon. The synthesis gas feed is contacted, under methanation conditions, with a catalyst comprising nickel oxide and aluminum oxide.
As can readily be determined from the above, there is an ongoing search for new and more efficient processes for producing synthetic fuel gas from both solid and liquid carbonaceous materials.